Semiconductor high-purity chemicals and ordinary chemicals are stored in a tank good in resistance to these chemicals. Hitherto it has been known in the art that: formed in general in this tank 70 are two pieces of mouth stopper sections 71 and 71a; and, plugs 72 and 72a are mounted on these mouth stopper sections 71 and 71a, respectively, wherein each of the plugs 72 and 72a is provided with its corresponding plug section not shown in the drawings (FIG. 8). These plugs 72 and 72a function as lids for closing the mouth stopper sections 71 and 71a, respectively. Of these plugs 72 and 72a: one serves as a liquid path connecting piece 72; and, the other serves as a gas path connecting piece 72a. Connected with the liquid path connecting piece 72 is a siphon tube 73 which reaches an area in the vicinity of a bottom section of the tank 70.
In retrieving the liquid stored in this tank 70, first of all, plug caps having been mounted on the plug sections of the plugs 72, 72a provided in the mouth stopper sections 71, 71a in the tank 70 are removed. After that, each of sockets 75, 75a having been connected with a hose 74 is connected with each of the plug sections of these plugs 72, so that the liquid contained in the tank 70 is retrieved and supplied to the hose 74 through the siphon tube 73 by using a pump P. At this time, in order to prevent the interior of the tank 70 from falling in negative in pressure, an inert gas is supplied to the tank 70 from a hose 74a having been connected with the plug section of the other plug 72a. 
Hitherto the applicant of the present invention has proposed a connector (a type of which is one shown in FIG. 1 in Japanese Patent application Laid-Open No.: 2004-163395 gazette), wherein the applicant of the present invention has proposed the connector to be attached to a liquid tank by compactly integrate two types of plugs. The connector is characterized in that: the connector is constructed of a plug fixedly mounted on the tank and a socket connected with the plug; the plug is provided with a liquid path and a gas path; and, the socket is provided with a liquid path communicated with the liquid path and also provided with a liquid path connecting piece communicated with the liquid path, and further provided with a gas path communicated with the gas path and also provided with a gas path connecting piece communicated with the gas path.
In either of the above-mentioned types, the plug cap may be fitted to the plug section of the plug. Thus, the liquid path and the gas path each having been formed in the plug section by means of the plug cap are blocked. Under such blocked condition, transportation and reservation thereof may be made.
In the above transportation and reservation of the tank, in order to prevent the chemical liquid or gas in the tank 70 from leaking out thereof, a seal ring is used in a peripheral surface or a ceiling surface in the interior of the plug cap and brought into intimate contact with such peripheral surface or ceiling surface. Thus, the liquid path or gas path of the plug is sealed up. As such a seal ring, an O-ring is generally used.    Patent document 1: Japanese Patent application Laid-Open No.: 2002-114242 gazette;    Patent document 2: Japanese Patent application Laid-Open No.: 2002-54782 gazette; and    Patent document 3: Japanese Patent application Laid-Open No.: 2003-163395 gazette.